Maybe someone bumped into the shelf and knocked the book down. Simple as that!
Well, in scary stories, it could be due to a curse. Maybe he's been hexed by some malevolent force, like a witch or a demon. It could also be because of some psychological trauma from a past event that gets triggered in the spooky setting of the story.
Well, it could be that the fanfiction is playing with the idea of redemption. Snape has a complex past, and his sarcasm might be a part of his prickly exterior. Hermione, being the empathetic character she is, might be drawn to him as she begins to understand his past through the fanfiction. The sarcasm could also be a sign of his intelligence, which Hermione respects. In the fanfiction world, their interactions might be crafted in such a way that she gradually falls for his sarcastic remarks as they lead to deeper conversations and a growing bond.
One reason could be a decline in the local population. If families moved away, there would be fewer students, and eventually, the school might have to close. Another reason could be financial problems. Maybe the school couldn't afford to maintain the building or pay the teachers. In some cases, a natural disaster like a flood or earthquake could damage the school so badly that it had to be abandoned.
One possible reason could be that there was a lack of proper supervision. If the adults around were not watching the kid carefully, the kid could easily get into trouble. Also, the well might be in an area where kids play, like near a field or a yard, and the kid was just exploring and unfortunately fell in.
One possible reason could be that the guest is an avid reader and wants to explore a new fictional world. Novels offer a great escape and the guest might be looking for that.
She might have suffocated if the sandbox collapsed on her. Maybe there was some sort of accident like a heavy object falling into the sandbox while she was in it.
Perhaps it was following a signal. There could be something in your house that emits a frequency or signal that the alien detected. It could be a simple electronic device or even something natural that gives off an energy that the alien mistook for something important. Or it might be that the alien is a bit of a mischief - maker, and it just randomly chose your house to have some fun and see how humans react.
Well, in a short story, she could be stuck in a well because she was playing a game. For example, she might have been playing hide - and - seek and thought the well was a great hiding place but then couldn't get out. Or perhaps she was trying to rescue an animal that had fallen into the well and ended up getting stuck herself. Also, it could be due to a natural disaster like an earthquake that made the ground unstable and she fell into the well that was already in a dilapidated state.
There could have been some sort of accident at the park, like a major ride malfunction that injured a lot of people. After that, people were too scared to come back, and the park's reputation was ruined. So, gradually, it was abandoned as no one wanted to visit it anymore. It could also be that the area around the park became less popular, for instance, if there were new industrial developments that made the area less appealing for families to visit.
Maybe it was a jinx. In the wizarding world, there are many spells that could make a broom go haywire. Some jealous rival in a Quidditch match could have cast a spell on his broom to make him fall.